Elevator dispatching with balanced passenger perception of waiting

ABSTRACT

A perceived waiting time for a hall call to be answered by a car is determined as a constant times the square ( 46 ) of the summation ( 45 ) of remaining response time ( 39 ) and the amount of time that has expired since the call was registered ( 38 ). The time that may be perceived by a passenger to travel to the passenger&#39;s destination is determined as a constant times the square ( 51 ) of the distance between an estimated destination floor and the floor of the call and a constant times an estimated number of new hall stops and committed hall stops that each car will make ( 47 ). Perceived service time is ( 52 ) the sum of perceived wait time and perceived travel time. Constants are adjusted so that a long waiting time will yield a quick travel time. Assignment of calls to cars ( 60 ) is in accordance ( 61 ) with the smallest summation of square ( 59 ) of perceived service times for all waiting up calls and down calls.

TECHNICAL FIELD

This invention relates to elevator dispatching in which the passenger'sperception of wait time prior to arrival of an elevator is balancedagainst the passenger's lesser perception of the travel time in theelevator, and selecting call assignments which provides a lowestfunction of overall perceived time for service.

BACKGROUND ART

In elevator dispatching, the passenger's perception of how long he orshe waits for an elevator to arrive has been determined to benon-linear, in the sense that the longer the passenger waits, the morethe passenger perceives that he or she has waited longer than the actualwait time. Stated alternatively, the degree of annoyance of waiting isnot a linear function of the wait, but increases, perhaps exponentially,with the elapse of time. In U.S. Pat. No. 5,304,752, preferentialpassenger service is allotted to an individual whose waiting time islonger than the waiting time of all passengers currently waiting forelevator service. In U.S. Pat. No. 4,244,450, the dispatcher uses anincreased function of waiting time, which increases with duration of thewait, to dispatch cars more in accordance with passengers' perception ofwaiting. In that patent, the assignment is based on providing a minimumsum of the overall perceived waiting time for all waiting passengers.Many systems provide for displays that will indicate the time remainingfor calls to appear, so that passengers are comfortable with the factthat response is impending; one example is U.S. Pat. No. 5,789,715.

DISCLOSURE OF INVENTION

Objects of the invention include: improving passenger perception ofwaiting and service times in an elevator system; dispatching elevatorsto respond to hall calls in a manner that causes passengers to perceiveminimum annoyance in waiting; and elevator dispatching which providesimproved passenger approval in the manner in which elevator calls areresponded to and serviced.

This invention is predicated, first, on our discovery that theperception of a long waiting time by a prospective elevator passenger isgreater for the time spent waiting for the arrival of the elevator carthan is the perception of the time that it takes to be served, that is,the travel time to the destination floor. The invention is predicatedalso in part on our discovery that overall perception, among allpassengers, of non-offensive times in being served by elevators is lowerif the controlling metric is the minimum of the sums of squares, orother exponential function, of the overall perceived delay of allpassengers in reaching the destination floor.

According to the present invention, a perceived waiting time, which is afunction of an expected time before a particular car can answer aparticular call, and a perceived travel time, which is a function ofweighted values of travel time to a destination floor (either estimatedor actual) and time to accommodate committed and expected stops, aresummed to provide a perceived service time; the before service waitingtime is weighted more heavily than the perceived travel time. Inaccordance with the invention further, for all possible sets ofassignments for all unanswered up hall calls and down hall callscurrently waiting in the elevator system, the perceived service time(waiting and traveling) for all outstanding hall calls are squared, andthe squares are summed; the set of assignments which provides thesmallest total sum of the squares is the set upon which assignments ofcars to answer calls is based.

The present invention may utilize neural networks to determine some ofthe components of those factors upon which call assignments are based.Specifically, remaining response time, conventionally referred to asRRT, may be determined by neural networks as disclosed in U.S. Pat. No.5,672,853. Other estimates, such as expected travel time and expectednew stop commitments for each car may also be determined, if desired,utilizing the neural network processing methodology disclosed in U.S.Pat. No. 5,672,853.

Other objects, features and advantages of the present invention willbecome more apparent in the light of the following detailed descriptionof exemplary embodiments thereof, as illustrated in the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional computer arrangementinterfacing with elevators, as an example of a system in which thepresent invention may be practiced.

FIG. 2 is a simplified logic flow diagram which is exemplary ofprocesses that may be utilized to practice the present invention.

MODE(S) FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, a signal processor 11 is illustrative of groupcontrollers that may allocate cars to respond to hall calls, utilizingaspects of the present invention. The processor 11 is responsive to aplurality of sensors 12, such as car weight sensors, and data signals13, such as car direction and door condition, provided to aninput/output (I/O) port 15 of the processor 11. Similarly, another I/Oport 18 is connected to a plurality of hall call buttons 19 resident onthe various floors of the building, a plurality of car call buttonpanels 20, one resident in each car, and a plurality of hall lanterns21, of which there are typically one or more at each floor landing. Theprocessor 11 includes a data bus 24, an address bus 25, a centralprocessing unit (CPU) 26, a random access memory (RAM) 27, and a readonly memory (ROM) 28 for storing the requisite elements of programs orroutines that can carry out the present invention.

In the routine of FIG. 2, it is assumed that up hall calls are processedfirst and then down hall calls are processed, after which all of thecalls together are processed as is about to be described.

Referring to FIG. 2, a hall call allocation program 30 is reachedthrough an entry point 31 and a first subroutine 32 (or a series ofthem) may perform heuristic screening of up hall calls against availablecars. This will eliminate cars, for instance, that are full and forwhich the call in question is ahead of the next floor call for that car.This will eliminate a car which has been assigned “taxi” service torespond to a very old hall call, cars that are in the wrong direction oftravel for their position in the building, or cars for which calls areoutside of a car's reach, due to some factor such as up peak sectorassignment. All of this is conventional, and not part of the invention.

A step 33 sets a floor counter, F, to one. Then, a test 36 determines ifthere is a hall call in the up direction on floor F. If not, a negativeresult of test 36 reaches a step 37 to increment F, and the next flooris tested in turn to see if there is a hall call on that floor.

If there is an up hall call on floor F, a step 38 determines the currentwait time for the up hall call on floor F as being equal to the presentclock time minus the time at which the call at floor F was registered.Then, a subroutine (or series of them) 39 will determine remainingresponse time for each car, C, for the up hall call on floor F, for allof the cars that are available to answer the up hall call on floor F.This may be preferentially be done in accordance with the aforementionedU.S. Pat. No. 5,672,853; otherwise, remaining response time can bedetermined in a number of other known ways.

A subroutine 40, or a series of them, then determines estimated newstops for all cars, C, available to answer the up call on floor F. Then,a car counter, C, is set to one in a step 41. A test 42 determines ifcar C is available to respond to the up call at floor F; if not, the Ccounter is incremented in a step 43 and the test 42 is once againreached. If the car is available, a step 45 determines the expected waittime, that is, the estimated time before car C will reach the up call onfloor F, as the remaining response time for car C to reach the up callat floor F (as determined in the subroutine 39) plus the time that thepassenger has currently waited (as previously determined in step 38).The perceived wait time is determined in a step 46 as some constant, K1,times the square of the expected wait time of step 45. However, afunction other than the square may be used.

An expected travel time is determined in a step 47 as the summation ofsome constant, K2, times the distance between the estimated destinationfloor and the floor F where the call is registered along with someconstant, K3, times the summation of the expected new stops and thecommitted stops of car C prior to reaching floor F. The estimateddestination floor may be the actual destination floor in a buildinghaving destination call buttons; or it could be a floor determined byhistorical date and call data for calls originating on floor F,utilizing artificial intelligence, with or without the assistance of theprocess just disclosed in U.S. Pat. No. 5,672,853 involving neuralnetworks. Or, the estimated destination floor may simply be one-half ofthe distance between floor F and the highest floor in the building.Whichever is utilized is irrelevant to the present invention.

A perceived travel time (PTT) is determined in a step 51 as a constant,K4, times the square of the expected travel time that was determined instep 47. However, a function other than the square may be used. Then, aperceived service time (PST), that is, the passenger's perception of theamount of time that it will take to get to his or her destination, isdetermined in a step 52 as the summation of the perceived waiting timeand the perceived travel time. Then the perceived service time issquared in a step 53. Of course, the steps 45-53 may all be combined ina single, long formulation instead of being performed one step at a timeas shown.

The constant K1 and the functions shown as squares in steps 46 and 51may either or both be adjusted relative to the constants K2-K4 and thenon-linear function, which is a square in step 51, so that a car thathas been assigned to a call which waits a long time for the car toarrive will be a car which will take the passenger most quickly to hisor her destination, thereby to lower the overall perception of waiting,including waiting for the elevator car to arrive and waiting for the carto deliver the passenger to his or her destination.

A test 54 determines if all of the cars have been tested for possibleservice to the up call at floor F. If not, the program reverts to thestep 43 where C is incremented, and the next car in turn is tested intest 42 to see if it is available to answer the up call at floor F. Ifit is, the process just described will repeat for that car; if not, thecar count is incremented and the next car in turn is tested.

Eventually, all of the cars will have been processed with respect to anup call at floor F and a test 55 will determine if all of the floorshave had their up calls processed. Originally, they will not have, so anegative result of test 55 causes the routine to revert to the step 37to increment F so that it can be determined in test 36 whether the nextfloor has a hall call in the up direction. If so, the process describedwill be repeated for this and subsequent floors until the test 55 isaffirmative, indicating that all up calls have been processed.

Then a series 56 of tests, steps and subroutines will be performed whichare the same as the tests, steps and subroutines 32-55, but for downhall calls.

Another aspect of the invention is forcing the system to try to equalizethe perceived service time across all passengers. Using the lowestsummation of the squares of the perceived service times for assignmentof cars to calls will select a set of assignments having service timeswhich are closer to each other. As an example, assume a PST of call Aequal to 10 and PST of call B equal to 10; the sum of the squares equals200. On the other hand, if the PST for call A equals 9, and the PST forcall B equals 11, the sum of the squares is 202, which is a lessfavorable overall scenario. If only the first power of the PSTs weresummed, the result would be 20 in each case, thereby not beingindicative of overall preferred performance. This is one aspect of thepresent invention. When the processing of all up calls and all down hallcalls is complete, the sums are taken of the squares of all perceivedservice times for all the possible assignments of cars to up calls anddown calls in a subroutine 59, for all possible sets of assignments ofall waiting up calls and down calls; cars will then be assigned to callsby a subroutine 60 based on that set of assignments which has the lowestsummation of squares of perceived service time, as determined by asubroutine 61.

1. A method of assigning selected ones of a plurality of elevator carsto answer hall calls outstanding in a multifloor building, comprisingthe steps of: for each car available to serve a particular hall calloutstanding in a building, (a) determining (45) an estimate of the waittime that will elapse after being registered before each said call willbe answered; (b) providing (46) a perceived wait time as a firstconstant times a first non-linear function of each said wait time; (c)determining (47) an estimate of the travel time that will elapse aftersaid each call is answered before reaching an estimated destination of apassenger registering said each call; (d) providing (51) a perceivedtravel time as a second constant times a second non-linear function ofeach said travel time; (e) providing (52) a perceived service time as asummation of said perceived wait time and said perceived travel time foreach said wait time and corresponding travel time; and (f) allocating(59) said available cars to respond to said outstanding hall calls basedon said perceived service times.
 2. A method according to claim 1wherein: said second constant and said second non-linear function areselected along with said first constant and said first non-linearfunction so that a hall call having a relatively long wait time for aparticular car will have a relatively short travel time to reach anestimated destination in said particular car.
 3. A method according toclaim 1 wherein said step (f) comprises: providing the square (53) ofeach said perceived service time; for all possible sets of assignmentsof all said up hall calls and down hall calls outstanding in saidbuilding, providing (59) a summation of said squares; and assigning carsto calls (60) in accordance with the one of said sets having the lowestof said summations (61).